Mmmm, all depends what you are looking for.
As far as aircraft goes, a good start is anything from Milton Shupe (& team), Bill Lyons has a heap of aircraft, most with a story. You can also 'theme' your sim to a Golden Wings or a Silver Wings style. For myself, I prefer the props & older aircraft, with very few jet liners in my sims.
You can also have more than one install, with themed aircraft & scenery.
We have had many a discussion regarding realistic versus immersion. Simming, as the late Garry Smith of Ford Tri-Motor Project fame, always said that simming is all about fun, facts & fiction. For realism, an option is to get hold of some of the so-called 'study level' aircraft, where you can learn all the nuts & bolts of the thing. I've gone for immersion, & I've seen that within a actual sim that our virtual club built, of an Avro Shackleton cockpit that fits on a trailer, using FS2004 & freeware scenery of my homeland, South Africa. We get actual pilots to 'fly' the static sim, & they get so immersed that they actually 'bump' themselves in their seat, anticipating touchdown.
If it's aircraft that you are interested in, just reply with the type that interests you, & we will get a list together for you.
Chris says very wise words.. set the sim up the way YOU want. We are all here to add a helping hand,